jQuery.fn.dataTableExt.aTypes.unshift(
    function ( sData )
    {
        var sValidChars = "0123456789-,";
        var Char;
        var bDecimal = false;
         
        /* Check the numeric part */
        for ( i=0 ; i<sData.length ; i++ )
        {
            Char = sData.charAt(i);
            if (sValidChars.indexOf(Char) == -1)
            {
                return null;
            }
             
            /* Only allowed one decimal place... */
            if ( Char == "," )
            {
                if ( bDecimal )
                {
                    return null;
                }
                bDecimal = true;
            }
        }
         
        return 'numeric-comma';
    }
);